Morphological Study of the Eustachian Tube in Mongolian Gerbil

Abstract

Background : Many animals such as chinchilla, guinea pig, rat and rabbit have been used for study of the otitis media and their morphology of the eustachian tube are well known. However, it is not easy to use these animals in Korea. Therefore, active morphological study of the eustachian tube related to otitis media have not been performed. The Mongolian gerbil is an easily maintained rodent which has* been useful for investigations of the ear canal cholesteatoma and inner ear. However, histologic study ´of the eustachian tube of Mongolian gerbil has not been established. Objectives : The purpose of this study was to-describe the light microgcopie morphology and the ultrastructure of the eustachian tube in Mongolian gerbil in order to prepare basic morphological data for the future animal study concerning pathogenesis of otitis media. Materials & Methods : Eight normal adult(90 to 120 days old) Mongolian gerbils (16 ears) were used for this study. Eustachian tube specimen was obtained after perfusion fixation and fixed. After 3 weeks of decalcification, paraffin block and EPON 812 block were made and sectioned. Those were observed under fight microscope and transmission electron microscope. Results : The cartilage and muscular structure(tensor vch palatini muscle, levator veli palatini muscle) of the eustachian tube of Mongolian gerbil were similar to those of other experimental animals. The total´ length of eustachian tube of Mongolian gerbil was relatively short and natural infection was rare.In the epithelium of the eustachian tube of Mongolian gerbil, four types of epithelial cells, ie ciliated, nonciliated, secretory cells and basal cells were identified like other experimental animals. On transmission electron microscopic findings, three types of secretory cells, ie, dark granulated, light granulated and mixed granulated cells were observed. The qubepitheial glandular structure was observed along the whole length of eustachian tube. Conclusion : In this study, we found that the morphology of the eustachian tube of Mongolian gerbil was similar to those of other experimental animals such as´ chinchilla, guinea pig, rat and we recognized that Mongolian gerbil is possible to be used as a good experimental model of eustachian tube study for otitis media research.